Patent GB-591896-A (GB)
Title: Manufacture of ethers of phenols
IPC: C07D213/65
Filed: 1944-06-09
Abstract: Phenol ethers are obtained by heating a substantially solid mixture of an alkali salt of an aryl mono-sulphonic acid or of b -pyridine sulphonic acid, and an inorganic base with an alcohol in the vapour phase in the absence of oxygen under such conditions that the ether formed volatilises during the reaction.  Specified aryl residues are derived from: benzene, toluene, m-xylene, naphthalene.  Specified alcohol residues are: methyl, ethyl, isoprpyl, isoamyl, cyclohexyl. The alcohol vapour may be introduced as such or it may be generated in situ from a derivative of the alcohol, e.g., methyl chloride, which decomposes under the conditions of the reaction to liberate the free alcohol. Specified inorganic bases are: a caustic alkali or other base, capable of forming a stable sulphite, e.g., an oxide, hydroxide or carbonate of an alkaline metal such as calcium or magnesium, or an alkaline metal carbonate such as sodium carbonate or a strongly basic salt such as tri-sodium phosphate, or mixtures of two or more of such bases.  Advantageously, when caustic alkali is so used, its proportion is not substantially in excess of the stoechiometric amount, and to the mixture of alkali and sulphonic acid may be added a solid substance which is substantially insoluble infused caustic alkali in a proportion sufficient to counteract frothing and swelling and to maintain the reaction mixture in a substantially solid condition.  Specified solid substances are: an oxide or hydroxide of an alkaline earth metal, a sulphite or sulphate of an alkali metal, finely powdered carbon or a mixture of two or more of these.  Advantageously, when caustic alkali is used as inorganic base, the reaction residue is treated with caustic soda to regenerate alkaline metal sulphonate and caustic alkali from alkali sulphite contherein, and worked up into a fresh reaction mixture. Similarly, when an inorganic base other than caustic alkali is used, the reaction residue is treated with a quantity of the corresponding sulphonic acid sufficient to yield by reaction with alkali sulphite the amount of alkali sulphonate required for a fresh reaction.  The sulphonic acid salt and inorganic base are preferably mixed very intimately in the form of solid, agglomerated masses.  To reduce the partial pressure of water vapour evolved during the reaction an excess of alcohol vapour may be used.  Advantageously, the reaction mixture contains both sodium and potassium in a proportion relatively to one another such that the atomic proportion of potassium ranges from about 23 to 45 per cent, especially from 40 to 45 per cent of the total atomic proportion of alkali metal present, and suitably in the form of a salt inert under the conditions of the reaction, e.g. potassium chloride.  When a mixture of calcium hydroxide with less than the theoretical quantity of caustic alkali is used as inorganic base, the reaction mixture is suitably heated at the different reaction temperatures appropriate to each of the two bases when used without the other.  The reaction may be conducted continuously by passing the solid reaction mixture and the alcohol through a reaction vessel in counter-current.  In examples: (1) potassium benzene sulphonate in aqueous solution is mixed with calcium hydroxide to form a slurry which is evaporated, heated with dry methyl alcohol vapour yielding anisole condensate, and a reaction residue mixed with water, heated to expel the recoverable methyl alcohol and to causticize a part of the alkali sulphite present, supplemented with a further quantity of benzene sulphonic acid treated with sufficient calcium hydroxide to form a fresh reaction slurry; (2) potassium benzene sulphonate, sodium benzene sulphonate and caustic soda in aqueous solution are mixed with calcium hydroxide to form a slurry which is evaporated, heated with dry methyl alcohol vapour to yield an anisole condensate, and a reaction residue which is treated as in 1; (3) the sodium salts of the mixture of sulphonic acids obtained by sulphonating m-xylene with strong sulphuric acid are treated with caustic potash and calcium hydroxide to obtain a dry granular mass, which is treated as in (1) with methyl alcohol; (4) proportions of potassium naphthalene-a -sulphonate, caustic soda and calcium hydroxide in the molecular ratio of 1 to 1.2 to 1 are worked up as in (1), heated with dry methyl alcohol, firstly to cause the caustic soda and later the calcium hydroxide to react, yielding a -naphthyl methyl ether and a reaction residue which is worked up into a reaction slurry as in (1); (5) potassium benzene sulphonate, sodium benzene sulphonate, caustic soda and calcium hydroxide are mixed and heated as in (4) with dry ethyl alcohol to yield a phenetole condensate; (6) a mixture of potassium benzene sulphonate, caustic soda, and calcium hydroxide is heated with isoamyl alcohol to obtain isoamyl phenyl ether; (7) a mixture of potassium benzene sulphonate, caustic soda and calcium hydroxide is heated with cyclohexanol to obtain cyclohexyl phenyl ether; (8) a mixture of sodium b -pyridine sulphonate, caustic potash caustic soda and calcium hydroxide are heated with methylalcohol to obtain b -pyridyl methyl ether. Specification 559,642 is referred to.